The invention relates generally to roadway monitoring systems and more specifically to in-road, wireless roadway monitoring systems.
The level of traffic congestion on roadways is a serious problem imposing excessive burdens upon commuters in terms of commute time, stress, fuel consumption and vehicle wear and tear. Reports suggest that the amount of congestion-induced delay experienced by the average commuter in a large city such as Los Angeles or Boston has more than doubled over a span of less than two decades.
Given the practicalities of driving habits and limited capital resources, the most realistic near-term approaches to reducing road congestion involve improvements to current roadways. For example, an initiative underway at the National Intelligent Transportation Systems (ITS) utilizes information technology to make better use of existing roads. One particularly compelling system envisioned by ITS workers is the Automated Traveler Information System (ATIS). Before embarking on a trip, drivers could consult a Web page to obtain accurate trip time estimates for various departure times and modes of transportation. Upon embarking, a dynamic route guidance system would provide them with turn-by-turn directions based on up-to-the minute information about roadway speeds and congestion levels.
At the very least, this type of system would allow drivers to make better route decisions, to be confident that they were taking the most efficient route, and to plan their activities around traffic delays. One of the largest obstacles to the implementation of this type of system is the shortage of accurate, real-time traffic data. Currently available traffic sensor systems (e.g., video, sonar, radar, inductive, magnetic, capacitive, polyvinylidine fluoride (PVDF) wire, pneumatic treadle) use significant electrical power, so each sensor must be connected to a power distribution network. For sensors that are installed on electrical poles (video, sonar, radar), the installation cost per sensor can be several hundred dollars. For cabled sensors that are installed in the roadway receiving power and/or communicating via cables, (inductive, magnetic, PVDF wire, capacitive, pneumatic treadle) the installation cost per sensor can be several thousand dollars. Inroad sensors are currently utilized in certain xe2x80x9ctrouble spotsxe2x80x9d because they are very accurate, provide direct information with very little ambiguity, can monitor road conditions (e.g., presence of ice), and do not require a human operator. But their high cost discourages the widespread deployment that would be necessary for large-scale monitoring networks.
In general, the present invention provides a low-power, wireless, in-road traffic sensor system using sensors that are small, low-cost, and rugged. The sensors may be capable of measuring the speed of passing vehicles, in addition to measuring information about roadway conditions, e.g., wet or icy. Each sensor may be configured to consume so little power that it can operate from a small internal battery for up to 10 years. The low cost and ease of installation allows communities to outfit entire roadway systems, thus providing a viable near-term solution for managing roadway traffic congestion.
Accordingly, in a first aspect, the invention comprises a wireless roadway sensor configured for installation beneath a roadway surface. The sensor includes a sensing element capable of sensing roadway conditions, such as the presence of a vehicle on the roadway, an average speed of vehicles on the roadway, types of vehicles on the roadway, and water and/or ice on the roadway. The sensor also includes a wireless transmitter for periodically broadcasting sensed information to a remote destination.
In one embodiment, the sensor includes a magnetic sensing element for sensing vehicles on the roadway through perturbations in the ambient magnetic field. In another embodiment, the sensor includes a capacitive sensor element for sensing precipitation on the roadway through the electrical measures, such as the dielectric constant and the conductivity at the roadway surface. In yet another embodiment, the sensor includes a temperature sensor element for sensing the temperature of the roadway and, in conjunction with the precipitation sensor, inferring the presence of road-surface ice.
In another aspect, the invention comprises a wireless roadway sensor that includes a sensing element for sensing a roadway condition and a wireless transmitter for transmitting the sensed information to a remote destination. The wireless transmitter communicates with the sensor and periodically broadcasts the sensed information on a communication channel using a randomized multiplexing scheme. The randomized multiplexing scheme allows the channel to be shared with other sensors broadcasting in accordance with the scheme.
In one embodiment, the transmitter is a narrowband radio-frequency (RF) transmitter. In another embodiment, the transmitter is configured to modulate a RF carrier signal using frequency-shift-keying modulation. In yet another embodiment, the sensor is configured to use a receiverless protocol, further reducing its power consumption.
In yet another aspect, the invention comprises a wireless roadway sensing and information-integration system. This system includes multiple sensors distributed across a roadway system. The sensors are organized into sets each including one or more sensors. Each of the sensors includes a sensing circuit for sensing at least one roadway condition and a wireless transmitter for periodically broadcasting the sensed information. The system also includes a number of concentrators for receiving the sensor broadcasts, whereby each concentrator receives broadcasts from the sensors of one of the sets. The system also includes a computer in communication with the concentrators. The computer is configured to accumulate and organize the sensed information obtained by the sensors.
In one embodiment the computer determines traffic volume through vehicle counts reported by the sensors. In another embodiment, the computer determines alternate routes responsive to traffic congestion being sensed along an initially-planned route. In yet another embodiment, the computer includes a Web server communicating over the Internet for providing the sensed roadway information responsive to Web client requests.
In yet another aspect, the invention comprises a method for controlling traffic whereby a sensor is installed beneath a roadway surface for sensing a roadway condition. The sensor, in turn, transmits information relevant to the sensed condition through periodic wireless broadcasts to a remote receiver for actuating a traffic-controlling device.